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The Great Ape Trust in Des Moines, Iowa, is home to seven bonobos -- a close relative of the chimpanzee -- and three orangutans. But if you think Iowa might be a strange place for them to live, don't say it out loud … these apes understand English.

Really. No kidding.

Watch more on this story tonight on 'Nightline' tonight at 11:35 p.m. EDT.

You can talk to the apes, and they know what you are saying.

The residents of the Great Ape Trust are part of groundbreaking language research where the apes are being taught to communicate with humans by pressing 350 lexigrams -- symbols that appear on a screen and represent thoughts and objects.

The superstar is 26-year-old Kanzi, whom Bill Fields has been working with for years. To communicate, Fields speaks to Kanzi, who then points to the lexigrams to respond and demonstrate a level of understanding.

"Qualitatively, there is no difference between Kanzi's language and my language," Fields said. "It's a matter of degree."

The key to ensuring they grasp the language, the researchers said, is to start teaching them when they are young, just like you would with human babies.

"Language is culturally acquired. Its not learned," said Fields. "It's acquired in the immediate postnatal antogyny of the organisms life. The only organism capable of learning language are babies."

They've been communicating with bonobos through the keyboard for almost three years, relying on a technique developed in 1971 and also used at the Primate Research Institute at Kyoto University and other facilities.

At the Great Ape Trust, researchers said the apes would likely never be able to vocalize words like humans; they are limited by the range of their vocal chords among other things.

However, Fields swears he has heard Kanzi try to say "thank you."

'Surprise' From an Interview With an Ape

When they begin to work with the apes, some pick up the vocabulary quickly while others never acquire the language.

Rob Shumaker has known Azy, a majestic, huge male orangutan, for more than 20 years. He talks to Azy, just like he would speak to one of his children, or a longtime friend.

"When I'm around them we just kind of talk normally," he explained. "I use my normal vocabulary, my normal voice my normal gestures."

Sound beyond belief? During a visit to the Great Ape Trust, I sat down with Kanzi the Bonobo -- the first Ape I have ever interviewed.

I read Kanzi a series of words, and then without fail, he hit the corresponding lexigram symbol on a touch screen.

I said "Egg."

He pressed "Egg."

I said, "M and M."

He pressed "M and M."

Then Kanzi took control of the conversation and pressed the symbol for "Surprise!"

Needless to say, I was quite surprised, having never actually spoken to an ape before.

But Kanzi was pointing to a box of candy that I was sitting near. That is the surprise that he wanted.

Moments like this are proof that these conversations help scientists learn about apes, from the apes themselves.

"If we have some common means of communicating with each other," said Shumaker , " we suddenly have exponentially large number of topics that we can explore."

"It allows Kanzi to tell me if his stomach hurts, his head hurts or if he'd like to be alone or if he's afraid or scared," Fields added.

Speaking Up for Their Survival

There's another possible impact of the communication with these apes: These celebrity apes may help raise awareness of the plight of apes in the wild.

Shumaker said there is an estimated 10,000 to 50,000 bonobos left in the wild, and 50 - 55,000 orangutans in the wild, so raising awareness of just how smart these creatures are might encourage the public to take their problems more seriously.

"The research we conduct here powerfully informs people about the nature of great ape intelligence," Shumaker said. "We know that humans and great apes share far more than they differ. I think we have to recognize that. If that does not compel us to preserve great apes in the wild, I don't know what can."

The insight into ape learning might also give some insight into human development.

"It tells us about how we learn everything," said Fields, "what the antecedents are to the kind of powerful learning that could occur in humans."

Sometimes the similarities to humans are downright eerie. When I asked Kanzi if he wanted coffee, he enthusiastically shook his head up and down.

Bonobos share 98 percent of their DNA with humans -- they also apparently share a love of decaf caramel machiatos.